It also comes as Charlotte, North Carolina-based Wachovia plans significant branch expansion in California and Texas, the most populous US states. Wachovia said it plans by 2010 to build at least 300 green branches nationwide.

The bank said it may save about US$80,000 in construction costs for each green branch, and see 20 percent lower operating costs.

"It makes sense on several fronts," Patrick Mumford, the bank's head of environmental affairs, said in an interview. "It's an extension of our commitment to communities. Our customers and employees are also interested in how Wachovia responds to environmental change."

A formal announcement of the program is expected Thursday.

The first green branches will open in Los Angeles, Orange, Riverside and Santa Barbara counties beginning in November.

Wachovia made a major push into California last October when it paid about US$24.2 billion for Oakland's Golden West Financial Corp., the second-largest US savings and loan.

Mumford said customers probably will not notice many differences between green branches and traditional branches, apart perhaps from more natural light and better air quality.

He said Wachovia plans to post educational displays in the branches, and station bicycle racks near the front doors.

Mumford said the bank is looking at ways to retrofit some of its 3,400 existing branches, including about 285 it added when it bought Golden West.

New York-based Citigroup pledged this month to commit US$50 billion over the next decade to environmental projects.

Charlotte-based Bank of America pledged US$20 billion over 10 years to support environmentally friendly activities and reduce global warming. It is also building energy-efficient towers in Charlotte and near Times Square in New York.